ASTRO: M27 in [SII], Ha and [OIII]

this is adding sulfur and oxygen to the previously-released halpha image of
M27 taken a few days ago.

last night the marine layer finally cooperated long enough for me to get
some sulfur and oxygen data. I really want to take 6 hours in each filter
but thus far have had to get by with only two hours per filter.

So I am at 6 hours instead of 18 hours, which is the goal.

The image was taken using the Stinger 450 classical cassegrain, and the
IMG1024S Dream Machine camera.

Total exposure time is 6 hours 20 minutes (6x 20 minutes for Sulfur, Oxygen
and 7 x 20 minutes for Halpha)

http://www.narrowbandimaging.com/m27...2hao3_page.htm

One thing that is noteworthy: The Stinger is not designed to support a FOV
as big as I get using the DM with the focal reducer. It vignettes a bit in
the corners. In the past the vignetting has been a bother, even in the final
calibrated images. I have recently made a few operational changes in the
way I am shooting my flats and have discovered the flats now take care of
the vignetting. This was an unexpected benefit, as I was pretty sure the
corners were a pretty hopeless cause due to the baffle design etc

rdc